If a ship sails under a flag of convenience, it is registered in a country where taxes, etc, are lower than in the country it comes from, so if someone does something under a flag of convenience, they attempt to avoid regulations and taxes by a similar means.

If you up the ante, you increase the importance or value of something, especially where there's an element of risk as the term comes from gambling, where it means to increase the stake (the amount of money bet).